Characterization of the Protective Immune Response to Respiratory Syncytial Virus. Goal: To identify RSV F and G protein epitopes involved in producing protective immunity following RSV infection. Respiratory syncytial virus is the most common cause of lower respiratory tract disease in young children worldwide. The F and G glycoproteins of this virus are known targets of a protective immune response. However, immunity is incomplete and repeated infections with viruses of the homologous or heterologous subtype occur despite development of anti-F and anti-G antibodies. In addition, antibodies that neutralize extracellular virus may not be able to inhibit fusion or cell-to-cell spread. These findings suggest that human B cell responses elicited after natural infection may be deficient in antibodies that prevent virus-receptor interactions. In order to understand virus-cell interactions required for virus infectivity, studies were initiated to identify the receptor(s) used by RSV. The binding of RSV F and G viral envelope glycoproteins to cell surface glycosaminoglycans was evaluated using heparin agarose affinity chromatography. Cell binding assays were used to evaluate binding to Vero, Hep-2 and A549 cells and the specificity of the interaction was evaluated by competitive binding and flowing treatment of cells with GAG lyases. Peptides were further evaluated to see if they represented epitopes recognized during human infection. During the last year linear heparin binding domain within RSV-F1 and F2 were mapped. Discontinuous sodium chloride gradients were also used to compare heparin-binding affinities of the envelope glycoproteins of virulent and attenuated RSV subgroup B strains. These studies showed that an attenuated subgroup B strain had higher affinity for heparin than did the virulent parental strain. Likewise, the attenuated virus was inhibited in vitro more efficiently by soluble heparin than the low passage virulent parent virus. The findings suggest that tissue culture adaptation can increase heparin affinity and this contributes to attenuation in vivo. Immunogenicity and Safety of Measles Virus Vaccine Strains. Goal: To identify the preferred age and schedule for measles immunization and to identify measles vaccine components associated with autoimmune responses. One of the major goals of the USPHS was the regional elimination of measles by the year 2000, a goal that was achieved due to an increase in immunization rates and implementation of a two-dose schedule. However, there are still some unanswered questions regarding optimal use of measles vaccines so that worldwide eradication is achieved. For example, research is needed in order to identify the safest and most effective measles vaccine for immunization of immunocompromised children, e.g., with HIV infection. If infected with measles virus, these immunocompromised children could suffer serious disease or be a source of persistent shedding and spread of measles virus and impede the eradication effort. In addition, healthy infants born to immunized mothers lose passively acquired measles antibody at an early age, and become vulnerable to infection before their first birthday. It is not known if young infants can be routinely and effectively immunized with current measles vaccines. Progress. This laboratory provided support for clinical studies conducted by the following primary investigators: 1. Drs. Rosa Wong-Chew with Jose Valdespino, Hayley Gans, Yvonne, Maldonado, and Anne Arvin, Stanford: Evaluated subcutaneous vs. intranasal measles vaccination using standard titer Edmonston-Zagreb vaccine in 12 month old infants in Mexico. This study demonstrated that B and/or T cell immunity was elicited in a majority of infants irrespective of route of administration. A manuscript based on these findings has been accepted for publication 2. Dr. Afzal, NIBSC, invited this laboratory to participate in a collaborative study to evaluate the use of RT-PCR in the detection of measles virus sequences in tissues from individuals with inflammatory bowel disease. These studies showed that PCR sensitivity varied widely by laboratory. All tissues from individuals with inflammatory bowel disease were found to be free of measles virus genome when tested by RT-PCR. These results were published in Journal of Medical Virology. This project incorporates FY2002 projects 1Z01BK002019-10 and 1Z01BK002020-10.